The impact of the turmoil in Greece on sharemarkets is a classic example of how the emotions of fear and greed create volatility.
When shares start to drop in value, investors can become fearful of sustaining further losses. This leads to panic selling, which further fuels the fear.
Eventually, a turning point is reached when less risk-averse investors spot the potential for gain. Increased buying activity pushes prices up, and fear is diminished.
The outcome of this process is that risk-averse investors suffer losses while gains go to those who are less risk-averse.
Significant events can have a ripple effect on markets, just like a pebble being thrown into water.